As an aluminum alloy wire for a conductor, Patent Literature 1 discloses an aluminum alloy wire that has a composition including 0.2% or more to 1.0% or less of Mg, 0.1% or more to 1.0% or less of Si and 0.1% or more to 0.5% or less of Cu, and including Al and impurities as the balance, in which the ratio by mass of Mg/Si satisfies the following: 0.8≤Mg/Si≤2.7.
When this alloy wire is produced through a process of “casting (continuous casting or billet casting), rolling, solution treatment, aging treatment, wire drawing, and final thermal treatment”, the alloy wire can be produced as an aluminum alloy wire having a tensile strength of 120 to 200 MPa, an elongation of 10% or more, an electroconductivity of 58% IACS or more, and a diameter of 0.2 to 1.5 mm.
In such techniques, requests of making aluminum electric wires smaller in diameter have been enhancing in the light of recent needs that automobiles should be made lighter. A standard of aluminum electric wires for automobiles is JASO D603. According to this standard, the minimum electric wire size is 0.75 sq (a sectional area of 0.75 mm2), and performances of an element wire that constitutes a conductor are prescribed as follows: a tensile strength of 70 MPa or more, an elongation of 10% or more, and an electroconductivity of 58% IACS or more.
In the case of referring to the respective sizes of copper electric wires for automobiles that are prescribed in JASO D611, as conductor sizes thinner than the above-mentioned size 0.75 sq, the following specifications in the future are foreseen: 0.5 sq (a section area of 0.5 mm2), 0.35 sq (a section area of 0.35 mm2), 0.22 sq (a section area of 0.22 mm2), and 0.13 sq (a section area of 0.13 mm2).
In general, as the size of a conductor is made smaller, the load resistance of the resultant electric wire becomes lower. Thus, when such a thin conductor is supplied, it is necessary to make an element wire therefor high in strength. In the case of, for example, a conductor size of 0.5 sq or less, the following is necessary in order that an electric wire having this conductor size can gain a load resistance performance equivalent to that of an electric wire having a conductor size of 0.75 sq: an element wire for the electric wire has a tensile strength of 100 MPa or more. Furthermore, in the case of a conductor size of 0.35 sq, an element wire therefor needs to have a tensile strength of 150 MPa. Such an element wire is required not only to be increased strength in this way, but also to have, as a conductor for electric wires for automobiles, an appropriate elongation and electroconductivity.
It is stated that as the aluminum alloy wire suggested in Patent Literature 1, an aluminum alloy wire can be produced having a tensile strength of 120 to 200 MPa, an elongation of 10% or more, an electroconductivity of 58% IACS or more, and a diameter of 0.2 to 1.5 mm as described above. However, when this alloy wire is used as a conductor for an aluminum electric wire thinner than 0.75 sq, which is the above-mentioned size, it is concerned that the alloy wire is insufficient in element wire strength. As described hereinbefore, an aluminum alloy wire for a conductor has been required which satisfies all requests that the wire should have a high strength, a sufficient elongation, and a sufficient electroconductivity.